Selective effects of oxygen free radicals on excitation-contraction coupling in ventricular muscle: Implications for the mechanism of stunned myocardium

Wei Dong Gao, Yongge Liu, Eduardo Marban

Research output: Contribution to journalArticle

Abstract

Background: Oxygen free radicals (OFRs) have been implicated in the pathogenesis of myocardial stunning, but the precise mechanism by which OFRs foster stunning remains unclear. We investigated the pathophysiology of the contractile dysfunction that occurs after direct exposure of OFRs to cardiac muscle and compared the results with the pathophysiology of stunned myocardium. Methods and Results: Trabeculae from the right ventricles of rat hearts were loaded iontophoretically with fura-2 to determine [Ca2+](i). Steady-state force-[Ca2+](i) relations were obtained by rapid electrical stimulation in the presence of ryanodine. Two exogenous OFR-generating systems were used; H2O2+Fe3+-nitrilotriacetic acid (H2O2+Fe3+) to produce hydroxyl radical, and xanthine oxidase+purine (XO+P) to produce superoxide. In muscles exposed to H2O2Fe3+ for 10 minutes, both twitch force and Ca2+ transients were decreased (eg, in 1.5 mmol/L external [Ca2+], force decreased from 41±7 to 23±4 mN/mm2, P2+ transient amplitude from 0.96±0.09 to 0.70±0.05 μmol/L, P2+ activated force (F(max)) decreased slightly, from 103±5 to 80±12 mN/mm2 (P=NS). Neither the [Ca2+](i) required to achieve 50% of F(max) (Ca50) nor the Hill coefficient was changed. In muscles exposed to XO+P for 20 minutes, twitch force was reduced (in 1.5 mmol/L external [Ca2+]) from 50±9 to 39±8 mN/mm2 (P2+ transients, on the other hand, were not affected, F(max) decreased insignificantly from 100±16 to 81±14 mN/mm2. Ca50 increased from 0.71±0.06 to 1.07±0.07 μmol/L (P2O2+Fe3+ free radical-generating system reduces activator Ca2+ availability, whereas XO+P decreases the Ca2+ sensitivity of the myofilaments. Exogenously generated OFRs, particularly those produced by XO+P, mimic the effects of myocardial stunning on cardiac excitation- contraction coupling.

Original languageEnglish (US)
Pages (from-to)2597-2604
Number of pages8
JournalCirculation
Volume94
Issue number10
StatePublished - 1996

Fingerprint

Myocardial Stunning
Excitation Contraction Coupling
Free Radicals
Reactive Oxygen Species
Xanthine Oxidase
Muscles
Nitrilotriacetic Acid
Ryanodine
Myofibrils
Fura-2
Superoxides
Hydroxyl Radical
Electric Stimulation
Heart Ventricles
Myocardium

Keywords

  • calcium
  • free radicals
  • myocardial contraction

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Selective effects of oxygen free radicals on excitation-contraction coupling in ventricular muscle : Implications for the mechanism of stunned myocardium. / Gao, Wei Dong; Liu, Yongge; Marban, Eduardo.

In: Circulation, Vol. 94, No. 10, 1996, p. 2597-2604.

Research output: Contribution to journalArticle

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abstract = "Background: Oxygen free radicals (OFRs) have been implicated in the pathogenesis of myocardial stunning, but the precise mechanism by which OFRs foster stunning remains unclear. We investigated the pathophysiology of the contractile dysfunction that occurs after direct exposure of OFRs to cardiac muscle and compared the results with the pathophysiology of stunned myocardium. Methods and Results: Trabeculae from the right ventricles of rat hearts were loaded iontophoretically with fura-2 to determine [Ca2+](i). Steady-state force-[Ca2+](i) relations were obtained by rapid electrical stimulation in the presence of ryanodine. Two exogenous OFR-generating systems were used; H2O2+Fe3+-nitrilotriacetic acid (H2O2+Fe3+) to produce hydroxyl radical, and xanthine oxidase+purine (XO+P) to produce superoxide. In muscles exposed to H2O2Fe3+ for 10 minutes, both twitch force and Ca2+ transients were decreased (eg, in 1.5 mmol/L external [Ca2+], force decreased from 41±7 to 23±4 mN/mm2, P2+ transient amplitude from 0.96±0.09 to 0.70±0.05 μmol/L, P2+ activated force (F(max)) decreased slightly, from 103±5 to 80±12 mN/mm2 (P=NS). Neither the [Ca2+](i) required to achieve 50{\%} of F(max) (Ca50) nor the Hill coefficient was changed. In muscles exposed to XO+P for 20 minutes, twitch force was reduced (in 1.5 mmol/L external [Ca2+]) from 50±9 to 39±8 mN/mm2 (P2+ transients, on the other hand, were not affected, F(max) decreased insignificantly from 100±16 to 81±14 mN/mm2. Ca50 increased from 0.71±0.06 to 1.07±0.07 μmol/L (P2O2+Fe3+ free radical-generating system reduces activator Ca2+ availability, whereas XO+P decreases the Ca2+ sensitivity of the myofilaments. Exogenously generated OFRs, particularly those produced by XO+P, mimic the effects of myocardial stunning on cardiac excitation- contraction coupling.",
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T2 - Implications for the mechanism of stunned myocardium

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AU - Liu, Yongge

AU - Marban, Eduardo

PY - 1996

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N2 - Background: Oxygen free radicals (OFRs) have been implicated in the pathogenesis of myocardial stunning, but the precise mechanism by which OFRs foster stunning remains unclear. We investigated the pathophysiology of the contractile dysfunction that occurs after direct exposure of OFRs to cardiac muscle and compared the results with the pathophysiology of stunned myocardium. Methods and Results: Trabeculae from the right ventricles of rat hearts were loaded iontophoretically with fura-2 to determine [Ca2+](i). Steady-state force-[Ca2+](i) relations were obtained by rapid electrical stimulation in the presence of ryanodine. Two exogenous OFR-generating systems were used; H2O2+Fe3+-nitrilotriacetic acid (H2O2+Fe3+) to produce hydroxyl radical, and xanthine oxidase+purine (XO+P) to produce superoxide. In muscles exposed to H2O2Fe3+ for 10 minutes, both twitch force and Ca2+ transients were decreased (eg, in 1.5 mmol/L external [Ca2+], force decreased from 41±7 to 23±4 mN/mm2, P2+ transient amplitude from 0.96±0.09 to 0.70±0.05 μmol/L, P2+ activated force (F(max)) decreased slightly, from 103±5 to 80±12 mN/mm2 (P=NS). Neither the [Ca2+](i) required to achieve 50% of F(max) (Ca50) nor the Hill coefficient was changed. In muscles exposed to XO+P for 20 minutes, twitch force was reduced (in 1.5 mmol/L external [Ca2+]) from 50±9 to 39±8 mN/mm2 (P2+ transients, on the other hand, were not affected, F(max) decreased insignificantly from 100±16 to 81±14 mN/mm2. Ca50 increased from 0.71±0.06 to 1.07±0.07 μmol/L (P2O2+Fe3+ free radical-generating system reduces activator Ca2+ availability, whereas XO+P decreases the Ca2+ sensitivity of the myofilaments. Exogenously generated OFRs, particularly those produced by XO+P, mimic the effects of myocardial stunning on cardiac excitation- contraction coupling.

AB - Background: Oxygen free radicals (OFRs) have been implicated in the pathogenesis of myocardial stunning, but the precise mechanism by which OFRs foster stunning remains unclear. We investigated the pathophysiology of the contractile dysfunction that occurs after direct exposure of OFRs to cardiac muscle and compared the results with the pathophysiology of stunned myocardium. Methods and Results: Trabeculae from the right ventricles of rat hearts were loaded iontophoretically with fura-2 to determine [Ca2+](i). Steady-state force-[Ca2+](i) relations were obtained by rapid electrical stimulation in the presence of ryanodine. Two exogenous OFR-generating systems were used; H2O2+Fe3+-nitrilotriacetic acid (H2O2+Fe3+) to produce hydroxyl radical, and xanthine oxidase+purine (XO+P) to produce superoxide. In muscles exposed to H2O2Fe3+ for 10 minutes, both twitch force and Ca2+ transients were decreased (eg, in 1.5 mmol/L external [Ca2+], force decreased from 41±7 to 23±4 mN/mm2, P2+ transient amplitude from 0.96±0.09 to 0.70±0.05 μmol/L, P2+ activated force (F(max)) decreased slightly, from 103±5 to 80±12 mN/mm2 (P=NS). Neither the [Ca2+](i) required to achieve 50% of F(max) (Ca50) nor the Hill coefficient was changed. In muscles exposed to XO+P for 20 minutes, twitch force was reduced (in 1.5 mmol/L external [Ca2+]) from 50±9 to 39±8 mN/mm2 (P2+ transients, on the other hand, were not affected, F(max) decreased insignificantly from 100±16 to 81±14 mN/mm2. Ca50 increased from 0.71±0.06 to 1.07±0.07 μmol/L (P2O2+Fe3+ free radical-generating system reduces activator Ca2+ availability, whereas XO+P decreases the Ca2+ sensitivity of the myofilaments. Exogenously generated OFRs, particularly those produced by XO+P, mimic the effects of myocardial stunning on cardiac excitation- contraction coupling.

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